On Fri, Jul 30, 2010 at 2:08 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Robert Haas <robertmh...@gmail.com> writes:
>> .... Maybe something like this,
>> obviously with a suitable comment which I haven't written yet:
>
>> numeric_digits = (precision + 6) / 4;
>> return (numeric_digits * sizeof(int16)) + NUMERIC_HDRSZ;
>
> This is OK for the base-10K case, but there's still code in there
> for the base-10 and base-100 cases. Can you express this logic in
> terms of DEC_DIGITS and sizeof(NumericDigit) ? I think you might
> find it was actually clearer that way, cf Polya.
It appears to work out to:
numeric_digits = (precision + 2 * (DEC_DIGITS - 1)) / DEC_DIGITS
return (numeric_digits * sizeof(NumericDigits)) + NUMERIC_HDRSZ;
The smallest value for precision which requires 2 numeric_digits is
always 2; and the required number of numeric_digits increases by 1
each time the number of base-10 digits increases by DEC_DIGITS.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company
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